How to Check a Used Phone's Battery Health Before You Buy

Two screens, sixty seconds, before any money changes hands. On an iPhone 15 or newer running iOS 17.4 or later, open Settings > Battery > Battery Health. On a Pixel 8a or newer, open Settings > About phone > Battery information. Both give you the same four things: maximum capacity, cycle count, when the battery was manufactured, and when it was first used. Then, on any iPhone from the XR onwards, check Settings > General > About for Parts and Service History, because a cheap non-genuine replacement battery shows up there as "Unknown."

That is the whole check. What follows is what each number actually tells you, what to do when the phone is too old to show them, and the one physical sign that should end the meeting immediately.

The number that catches a stretched listing: date of first use

Maximum capacity is the number everyone quotes. Date of first use is the number that tells you whether the rest of the listing is honest.

Google defines it plainly on its Pixel battery page: the date of first use is "the date your phone was first turned on and began to use the battery." Apple surfaces the same field on iPhone 15 models and later. A seller who says they picked the phone up in March, against a first-use date two years earlier, is not describing a battery problem. They are describing a provenance problem, and it is worth asking about before you get to the price.

Manufacture date sits next to it and means something different: the date the cell itself was assembled, before it went into the phone. Read the two together. If the manufacture date is much newer than the phone model's launch, the battery has almost certainly been replaced at some point.

One honest caveat, because nobody else on the internet seems to say it: neither Apple nor Google publishes whether a battery replacement resets the first-use date. So treat a first-use date that closely tracks a recent manufacture date as a sign the battery was swapped, not as proof the phone is young. That is exactly what the next check is for.

Where to tap, by phone

Samsung's route is the least numeric of the three. You open the Samsung Members app, tap Support, tap Get Started under Phone diagnostics, then tap the Battery status icon. Samsung returns one of three words. Normal means no issues with the battery. Weak means efficiency may have decreased through use or environmental conditions. Bad means the battery life has significantly degraded and Samsung wants you in a service centre. On a used Galaxy, treat Weak as a discount and Bad as a walk-away or a battery replacement priced into the deal. Our full Android walkthrough covers the third-party options if the seller has not installed Samsung Members.

What counts as a normal number, and what does not

Both manufacturers have published the line, and it is the same line: 80 percent.

Apple states that batteries in iPhone 14 models and earlier are designed to retain 80 percent of their original capacity at 500 complete charge cycles under ideal conditions, and that iPhone 15 models and later are designed to hold that same 80 percent out to 1,000 cycles. Google sets its replacement recommendation on the same threshold from the other direction: replace the battery on a Pixel 3 through Pixel 8 Pro or Pixel Fold once it drops below 80 percent capacity or reaches 800 cycles, and on a Pixel 8a or later below 80 percent or 1,000 cycles.

So 80 percent is not the point where a phone stops working. It is the point where the manufacturer considers the battery to have finished the life it was designed for. A three-year-old phone sitting at 84 percent is behaving normally, not failing, which is the context our guide to what a given percentage actually means goes into properly.

Two things to keep in your head while you read the number. First, cycle count and capacity tell you different stories, and a phone can be low on one and high on the other, which our explainer on cycle counts unpacks. Second, maximum capacity is an estimate the phone calculates, not a reading off a lab instrument, and it moves around between checks. If the seller's screenshot from last week says 89 and the phone in your hand says 86, that is not necessarily anyone lying, as our piece on why battery meters jump and disagree explains.

Parts and Service History: the check almost nobody runs

This is the one that separates a careful buyer from an optimistic one, and it takes ten seconds. On an iPhone, go to Settings > General > About and scroll. If the phone has had a part replaced, Apple lists it there with a label. Apple's own documentation defines four:

• Genuine: "The repair was done using genuine Apple parts and processes."
• Used: "The part was already used or installed in another iPhone."
• Unknown: the replacement part "isn't a genuine Apple part," "isn't functioning as expected," "hasn't been verified and linked to your iPhone after the repair was completed," or "has been modified or is otherwise unable to be verified."
• Unverified: the logic board was previously replaced, which Apple warns "might affect your ability to use certain features on your iPhone, such as Apple Pay."

Coverage depends on how old the phone is. Apple reports all five tracked parts on iPhone 12 models and later, battery and display on iPhone 11 models, and battery only on iPhone XR, XS, XS Max and the second and third generation iPhone SE. Anything older than that shows nothing at all, which is itself worth factoring into the price.

An "Unknown" battery costs you twice. Once now, because a non-genuine cell may report health data that is inaccurate or simply unavailable, so the reassuring percentage on the previous screen may be describing a part the phone cannot verify. And once later, because Apple says plainly that "an Unknown part might affect the trade-in value of your device." You inherit that when you buy.

Look at the phone, not only at the screen

Put the phone face down on a flat table and press one corner. If it rocks, stop. Other tells: the screen or back glass sitting slightly proud of the frame, a gap opening along one edge, a case that will no longer seat properly. Those are the signs of a swollen battery, and iFixit's guide to handling one is unambiguous about what to do next: do not charge it, do not puncture it, and get it to someone qualified rather than putting it in a drawer.

A swollen battery is not a negotiating point. It is the end of the viewing.

If the phone has been sitting in a drawer

Plenty of second-hand phones are sold by someone who upgraded a year ago and forgot about the old one. That is usually fine, and sometimes better than a phone that has been charged twice a day since launch, but it changes what you are looking at. A phone that has been stored will often not power on instantly and may need a genuine stretch on a charger before it shows anything useful, and its first reading after waking up is the least trustworthy one it will ever give. We wrote the full version of this check in does a phone lose battery health sitting unused, and it applies directly to a viewing where the seller hands you a phone that has been off.

Practical version: if the phone was off when you arrived, do not accept the first percentage it shows you. Let it run for a few minutes, then look again.

The sixty-second checklist

1. Open the battery screen yourself. Do not accept a screenshot.
2. Read maximum capacity or the Normal/Reduced status, and read the cycle count if the phone shows one.
3. Read the date of first use and compare it against what the seller told you.
4. Check Settings > General > About for Parts and Service History on any iPhone.
5. Put the phone on a flat surface and check it does not rock.

If all five pass, you are buying a known quantity. If the battery is past 80 percent of its rated life but everything else is clean, that is a battery replacement priced into the offer, not a reason to leave, and our replace or replace-the-phone decision framework does that arithmetic.

And for the first few weeks with a second-hand phone, while you are still learning what its battery actually does on a normal day, it helps to know that powerbank rental networks exist in most European cities for the afternoon you misjudge it.

Frequently asked questions

What battery health percentage is acceptable on a used phone?

Above 85 percent is comfortable. Between 80 and 85 percent is usable and worth a discount. Below 80 percent, both Apple and Google consider the battery to have finished its designed life, so price in a replacement rather than treating the number as a dealbreaker.

Can a seller fake the battery health reading?

Neither Apple nor Google gives the owner an editable field for these values. They are reported by the phone about its own hardware. The real risk is not a typed-in number, it is a non-genuine replacement battery reporting health data the phone cannot verify, which is why Parts and Service History is a separate and necessary check rather than a nice-to-have.

Does a replaced battery show up anywhere?

On an iPhone XR, XS, XS Max, SE second or third generation, or anything from the iPhone 11 onwards, yes. Settings > General > About lists the part with a label of Genuine, Used, Unknown or Unverified. On Android there is no equivalent first-party repair record, so the manufacture date in Battery information is your best proxy on a Pixel 8a or later.

My used Galaxy does not show a percentage. What should I do?

Samsung does not publish a capacity percentage in Settings. Run the Samsung Members diagnostic instead and take the Normal, Weak or Bad verdict, then cross-check with how the phone behaves over a few minutes of screen-on use.

Is a phone with 85 percent battery health worth a discount?

Yes, but a modest one. A battery at 85 percent is within normal ageing for a phone that is two or three years old, so the fair adjustment is a share of a replacement cost some way down the line, not the full price of one today.

Should I buy a phone with an "Unknown" battery?

Only at a price that assumes you will replace the battery with a genuine one. Apple's own wording covers parts that are non-genuine, not functioning as expected, or unverifiable, and it warns the label can affect trade-in value. None of that is fatal, but all of it belongs in the price rather than in the surprise column.